(a) Field of the Invention
An exemplary embodiment of the present invention relates to a switch controller and a power supply including the same. Furthermore, the exemplary embodiment of the present invention relates to a method for driving the power supply.
(b) Description of the Related Art
An LED string includes a plurality of LED elements that are coupled in series. Conventionally, the leap of an LED current supplied to the LED string is sensed for constant current (CC) control.
Under a condition that a buck converter is used to supply the LED current, the LED current is influenced by variation of an input voltage, an inductor, and an output voltage.
For example, when an input voltage of the buck converter is lower than an output voltage, power is not supplied to the output terminal. In further detail, when the input voltage is determined by a sinewave and the output voltage maintains a constant level, a period during which the input voltage is lower than the output voltage is generated. During the period, no power supply is performed, and accordingly the LED current is changed according to the period.
In addition, a ripple of an inductor current is changed according to inductance of the inductor. For example, the ripple is increased as the inductance is decreased. The LED current is estimated as an average of the inductor current, and therefore the LED current is decreased as the ripple is increased.
As described, variations of the input voltage, the output voltage, and the inductor cause occurrence of an error in the LED current.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.